1. Field of Invention
The present invention relates to a data transmission technology for dynamically adjusting a PDU length according to the bit error rate when packets are transmitted over the network.
2. Related Art
3G refers to the third generation, which is an abbreviation of the third generation mobile phone. Compared with the first generation mobile phone system of Advanced Mobile Phone System (AMPS), the second generation mobile phone system of Global System for Mobile Communications (GSM), and 2.5G General Packet Radio Service (GPRS) constructed on the second generation mobile communication device, 3G provides a higher communication quality and a higher transmission capacity and transmission speed. Different from the usual mobile communication which is mainly applied in voice service, short message service, and value-added service, 3G can transmit dynamic images and high-definition frame. In terms of wireless communication technology, 3G utilizes radio frequency bands higher than before, and has the following main specifications, including Wideband Code Division Multiple Access (WCDMA) and Code Division Multiple Access 2000 (CDMA2000).
Currently, WCDMA is mainly applied in Universal Mobile Telecommunication System (UMTS) and 3G system in Japan. This technology makes the 3G mobile communication be optimized, and makes the 2 GHz frequency band be sufficiently used. The data communication function of the WCDMA is similar to that of a computer network, and the WCDMA is generally divided into four layers, namely, a physical layer, a transport network layer, a radio network layer, and a system network layer. When the data needs to be transmitted, the data is divided into a plurality of data packets with a certain length, and once the connection is established, the data packets are transmitted. If the data packets are seriously lost, the physical layer adjusts the transmission power or the spread factor through power control, so as to reduce the bit error rate (ber) and reduce the block error rate, thereby increasing the effective data transmission and reducing the packet loss rate. However, when an error occurs to most of the data packets, adjusting the transmission power or the spread factor requires enhancing the transmission power and thereby increasing the power consumption, which causes signal interference between users, indirectly influences the transmission quality, such that the overall packet loss rate is increased.